This present invention relates to a counterbalanced rear closure assembly for an automotive vehicle.
It is known in automotive vehicles to employ powered sliding closure panels for providing access to the interior of the vehicle through an opening in the vehicle roof or wall. Power sun roofs and power sliding doors are examples. Another is the xe2x80x9cclam shellxe2x80x9d end gate on 1972 and later full size General Motors station wagons where the window was opened by sliding up into the roof while the end gate was opened by sliding down below the floor. Recent development of a rear closure assembly for selectively opening and closing a rear opening of an automotive vehicle included a sliding rear panel which is opened by sliding upward over the roof to clear the rear opening of the vehicle body. A second sliding roof panel may then be opened by sliding the rear panel forward with the roof panel to open a roof opening in the rear of the vehicle body roof.
A powered cable drive arrangement for sliding the panels between closed and open positions requires substantially greater motor power for sliding the rear panel upward to the roof than for sliding both panels forward along the roof. Accordingly, a suitable counterbalance arrangement for assisting opening of the rear panel was desired to allow use of a lighter and lower powered motor for sliding the closure assembly panels.
The present invention provides a cable drive assembly that pushes the rear panel upward from a first closed position to a second position above the roof panel to open a rear opening of the vehicle body. The cable may then push both panels forward toward a third position to open a connecting rear opening in the roof.
The cable drive assembly is patterned after prior cable drives for sun roofs and the like. A motor drives a gear that engages mating toothed cables, one on either side of the gear, and pulls or pushes them through channels so as to slide an attached rear panel from a closed to an open position and return. On the opposite sides of the motor, free ends of the cables are guided into cable return tubes. These retain the inactive portions of the cables until the motor is reversed and the cable is driven in the reverse direction to close or open the associated panel.
A feature of the present invention is that the cable drive motor is mounted at the lower rear portion of a vehicle, below the rear panel to which the cables are directly attached. Thus, operation of the motor pushes against the lower end of the rear panel to slide it upward in order to open the panel by raising it above the roof. The motor may continue to push the panel further in order to drive the rear panel, together with the roof panel, forward to open the rear roof opening, thereby providing an open bed at the rear end of the vehicle. Thus, when the panels are in their closed positions, the free ends of the cables are received in the cable return tubes, which may be located within the body of the associated vehicle. Upon opening of the panels, the cables are drawn from the return tubes by the motor and the cables are pushed against the rear panel for opening the panels of the vehicle.
Another feature of the invention is that compression assist coil springs, placed inside the cable return tubes, are compressed when the vehicle rear panel is in its closed position. These springs apply a compressive force against the free ends of the cables so as to provide a counterbalance force against the weight of the rear panel. The spring force is applied to assist the motor in opening the rear panel by raising or pushing up the rear panel to the roof position.
A further feature is that the compression springs are made only long enough to assist movement of the panel from the closed position to a point near its raised position where the force required for moving the panel is reduced and forward sliding movement of the rear and roof panels requires less force than is required for lifting the rear panel to its raised position. Thus, the compression springs are able to be made shorter and stronger for counterbalancing the high forces of lifting the rear panel but provide no assistance to the motor for moving the panels forward when they are in or near their roof locations. The result is a more even application of motor power over the full travel of the rear and roof panels which allows a smaller drive motor to be used for sliding the panels.